Pot Size: 2.5"
Accepted Scientific Name: Cleistocactus strausii
Origin and Habitat:
Cleistocactus strausii, commonly known as the Silver Torch cactus, is native to the high-altitude regions of southern Bolivia and northern Argentina, where it grows between 1,500 and 3,000 meters above sea level. Its native environment is cool, arid to semi-arid, with strong sunlight, rocky soil, and wide temperature fluctuations between day and night. These cacti are well-adapted to mountainous slopes and open grassland outcrops, where they experience intense sun and periodic droughts, along with occasional light frosts due to the elevation.
Description:
Cleistocactus strausii is a columnar cactus that grows upright to 6–10 ft (72–120 in) tall and about 2–3 in wide. It forms multiple vertical stems covered in dense silvery-white spines, which give the plant a soft, woolly appearance. The cactus typically has 20–25 narrow ribs with small areoles bearing short, golden spines. In summer, mature plants produce tubular, slightly curved flowers that are 2–3 in long and bright crimson to magenta. The flowers emerge horizontally from the sides of the stems and rarely open fully, remaining partially closed.
Cultivation:
Zone: USDA 9–11
Temperature: Thrives at 10–30 °C; can tolerate short periods as low as –5 °C in dry conditions
Growth rate: Moderate; faster in warm conditions with strong light
Soil: Use a well-draining mix of 2 parts pumice to 1 part cactus soil or peat
Watering: Water thoroughly when soil dries out; reduce to minimal watering during winter dormancy
Fertilizing: Apply a diluted cactus fertilizer every 2–3 weeks from spring to mid Aug.
Light: Requires full sun to very bright indirect light; insufficient light causes stretching and weak growth
Pests and Diseases: Susceptible to mealybugs and spider mites; root rot can occur in overly moist, poorly drained soil
Propagation:
Easily propagated from stem cuttings taken in warm weather. Allow cuttings to callous for several days before planting in dry pumice-rich soil. Seed propagation is possible but slow.